Behind you, the waves of lava crest, Death hanging ten from an unearthly waxed surfboard of bones. Your 757 races down the last piece of the island not already consumed by the eruption. Just as you feel the elation of lift-off, a suicidal family of coconuts leaps into the port engine. It coughs a guttural rattle and the plane heaves left. You recover, complete all of the checklist items, and climb up to altitude. So, can you make it to your original destination 2000 miles away?

Your original flight plan calls for 44,500 pounds of fuel. The flight itself was supposed to use 32,700 pounds, from takeoff to landing. The extra is for contingencies like having to fly around for a while, shoot another approach, and go to a divert field. But is it enough to help out with a missing motor? You check the books and find out that it will take over 50,000 pounds of fuel to go the distance.

What? How can that be? You are now only feeding one engine, so the consumption should be less! Not so, grasshopper. You now have a large speedbrake where your left engine was, the remaining engine is operating at a higher rate to compensate, and you can't climb up into the high 30s where the efficiency is much greater. You're stuck around 20,000' in the thicker air.

This is one of the reasons that twin-engine aircraft operate under ETOPS rules in remote parts of the world. Once an engine is lost, there needs to be a suitable field within a certain distance from the aircraft so that it can land safely.

If the flight is shorter, say Los Angeles to Las Vegas, there would be little trouble making it. No pilot would do so, however, unless the origin weather was so bad that landing there poses a greater risk than driving a few hundred miles on one engine (and the destination is also the take-off divert field, which is a requirement when the weather at the departure field is very low).